This invention relates to the measuring of objects seen with the aid of a microscope.
It has been the practice in measuring small objects seen in the microscope to place or project the image of a fine fiduciary line onto the image plane of the microscope. The line is then adjusted with the aid of a micrometer screw into coincidence with the edge of the image of the object to be measured and then translated with the aid of the micrometer screw to a position of coincidence with the opposite edge of the object's image. The displacement of the fiduciary line between the first coincidence and the second gives the size of the object. The accuracy of such a measurement is limited by the uncertainity in positioning the fine fiduciary line in a position coincident with the edge of the image of the object being measured.
Another practice in measuring objects seen in the microscope has been to split the image of the object and to move the images relatively by means of a suitable micrometer screw. By observation of the dark area produced where there is overlap of the semi-transparent images and the bright background produced where there is separation of the images, coincidence of the edges of the two images can be determined. The displacement of the images between a position of total superposition with edge coincidence to a position in which the sides of the images are externally tangent gives the size of the object. The accuracy of such a measurement can be more accurate than the above-mentioned fiduciary line technique because of better visual cues, but with the added requirement of image-splitting optics.
Objects of the present invention are to provide an apparatus which enables measurements with high accuracy and convenience and with simple components in a manner offering improvement in certain applications over both of the mentioned techniques.